Patent GB-190708183-A (GB)
Title: Improvements in Alternating Current Dynamo-electric Machines
Inventor: MERSHON RALPH DAVENPORT
Filed: 1907-04-08
Granted: 1908-04-08
Abstract: 8183. Mershon, R. D. April 8. Armatures ; dynamos, regulating ; motors, controlling. -The powerfactor and starting of induction motors and generators are improved by connecting condensers and impedances across separate conductors or sets of conductors forming the secondary windings, the condensers being preferably of the electrolytic type. The invention is particularly applicable to induction motors provided with means for changing the number of poles of the primary windings. In the simplest arrangement, Fig. 1, bars d of a squirrel-cage winding are bridged by condensers c and inductances b, similar devices being arranged in series with one another and in parallel with devices of different character. The effect is improved by the addition of resistances a, although the latter are not essential. The resistances may be in aeries with the condensers and impedances. In a modification, Fig. 2, similar devices are connected with separate sets of windings which overlap, each winding being more or less unaffected by the stray fields of the others. In further modifications, the windings are divided into two or more overlapping sections, each section being shunted by complete sets of capacities, inductances, and resistances, as in Fig. 1. In the modification shown in Fig. 3, some condenser effect is obtained in a secondary member having shortcircuited windings e by using additional coincident windings f having capacities c in series with them and arranged in the same slots so that the two windings embrace substantially the same are. In the arrangement shown in Fig. 6, two sets of windings are employed, one of the windings to which the condensers are connected consisting of independent coils m of more than one turn each, while the other winding n is of the squirrel-cage type and is embedded in the rotor core so as to have a considerable stray field around it. In the arrangement shown in Fig. 8, an electrolytic condenser is mounted on the rotor shaft o to avoid the use of slip-rings &c. The condenser consists of an outer cylindrical casing p enclosing a series of perforated metal plates q insulated from the shaft by a sleeve r. The plates q may be of aluminium, and the electrolyte may consist of a solution of borax. The condenser plates are connected to the rotor coils by tappings s brought out through openings in the condenser casing or through the shaft. The shaft o is hollow to accommodate pipes t, u for circulating the electrolyte through the plates The pipes t, u are connected by means of a suitable coupling z with a pumping and cooling apparatus or the like v. The pipe t may be coiled round the stator h for cooling the latter, while the pipe u may be similarly disposed on the rotor. In the coudenser shown in Fig. 10, no liquid-circulating system is employed. The casing is provided with enlarged openings through which the shaft passes, and is carried by spiders w. The electrodes are provided with similar openings, and are supported by insulating-rods x. When the condenser is rotating, the electrolyte is distributed around the plates by centrifugal force. Sheets or packings of absorbent material may be interposed between the plates to absorb the electrolyte and prevent splashing. Alternatively, the casings shown in Figs. 8 and 10 may be stationary and only the electrodes rotated by the shaft.